1. Field of the Invention
The present invention relates to a coding apparatus and method, a decoding apparatus and method, an image processing system, an image processing method, a recording medium, and a program. More particularly, the present invention relates to a coding apparatus and method for preventing illegal coping using an analog signal, a decoding apparatus and method for use therewith, an image processing system for use therewith, an image processing method for use therewith, a recording medium for use therewith, and a program for use therewith.
2. Description of the Related Art
In recent years, digital recording and reproduction apparatuses for recording content such as television programs using digital signals on a recording medium such as an HD (hard disk) or a DVD (Digital Versatile Disk) have rapidly become popular.
As a result of the popularization of digital recording and reproduction apparatuses in which an HD and/or a DVD is used as a recording medium, it has become possible for a user who is a viewer to easily record television programs on a recording medium with a high quality.
On the other hand, there is an aspect in which, as a result of the widespread use of digital recording and reproduction apparatuses, content, such as television programs and movies, which is sold in the form of DVDs, can easily be illegally copied.
FIG. 1 shows an example of the configuration of an image processing system for reproducing content recorded on a recording medium, for displaying the content, and for recording the played content into another recording medium.
In FIG. 1, an image processing system 1 includes a reproduction apparatus 11 for reproducing image signals of content recorded on a recording medium such as an optical disk such as a DVD and for outputting a resultant analog image signal Van; a display 12 for displaying, as an image, the analog image signal Van output by the reproduction apparatus 11; and a recording apparatus 13 for recording the analog image signal Van on a recording medium such as an optical disk.
The reproduction apparatus 11 includes a decoding section 21 and a D/A (Digital-to-Analog) conversion section 22. The decoding section 21 decodes a coded digital image signal read from a recording medium (not shown) and supplies the resultant digital image signal to the D/A conversion section 22. The D/A conversion section 22 converts the digital image signal supplied from the decoding section 21 into an analog signal and outputs the resultant analog image signal Van.
The display 12 is formed of, for example, a CRT (Cathode-Ray Tube), an LCD (Liquid Crystal Display), or the like, and displays, as an image, the analog image signal Van from the D/A conversion section 22. This makes it possible for the user to view an image corresponding to the image signal recorded on a recording medium.
Furthermore, the analog image signal Van output from the reproduction apparatus 11 is also supplied (input) to the recording apparatus 13.
The recording apparatus 13 includes an A/D (Analog-to-Digital) conversion section 31, a coding section 32, and a recording section 33, and records the input analog image signal Van on a recording medium (not shown) such as an optical disk.
The analog image signal Van output by the reproduction apparatus 11 is input to the A/D conversion section 31. The A/D conversion section 31 converts the input analog image signal Van into a digital signal and supplies the resultant digital image signal Vdg to the coding section 32. The coding section 32 codes the digital image signal Vdg from the A/D conversion section 31 and supplies the resultant coded digital image signal Vcd to the recording section 33. The recording section 33 records the coded digital image signal Vcd on a recording medium.
In the image processing system 1 configured as described above, by using the analog image signal Van output from the reproduction apparatus 11, an image signal can be recorded on a recording medium differing from the recording medium from which a playback is performed. That is, there is a risk in that, by using the analog image signal Van output by the reproduction apparatus 11, (the image signal of) content is illegally copied.
Hitherto, in order to prevent illegal copying using such an analog image signal Van, when copyright protection is made, it is proposed that the analog image signal Van be subjected to a scrambling process and be output, or the output of the analog image signal Van be prohibited (refer to, for example, Japanese Unexamined Patent Application Publication No. 2001-245270).
Furthermore, a digital video apparatus is proposed in which a noise information generation section is provided in one of a compression decoding section on the playback side and a compression coding section on the recording side or both, and noise information to such a degree that it may not be identified during image playback in one process is embedded into digital video data, so that copying itself is possible, but if copying is repeated for a plurality of times, the image is deteriorated considerably, thereby substantially limiting the number of times of copying (refer to, for example, Japanese Unexamined Patent Application Publication No. 1998-289522).
However, in the method of subjecting the analog image signal Van into a scrambling process and outputting the signal or of prohibiting the output of the analog image signal Van as in Japanese Unexamined Patent Application Publication No. 2001-245270, a problem arises in that, although illegal copying can be prevented, a normal image may not be displayed on the display 12.
In the method of embedding noise information in the compression decoding section on the playback side or in the compression coding section on the recording side as in Japanese Unexamined Patent Application Publication No. 1998-289522, a noise information generation section and a circuit for embedding the noise information become necessary, presenting the problem that the circuit size increases.
Accordingly, a technique for preventing illegal copying using an analog image signal without causing problems, such as an image being not displayed or the circuit size becoming large, to occur, is proposed by the applicant of the present invention (refer to, for example, Japanese Unexamined Patent Application Publication No. 2004-289685).